MOTOR TRUCK SERVICE MANUAL
COOLING SYSTEM
GENERAL
ANTIFREEZE - PERMANENT TYPE
The permanent type automotive antifreeze
Where considerable cooling system service is
commonly used today has been developed to a high
performed, good procedure would be to keep a supply of
point of reliability. This type antifreeze often referred to
premixed antifreeze on hand for makeup purposes. In
as "ethylene glycol base antifreeze, " is now used in
systems using permanent antifreeze, most coolant loss
practically all cooling systems and in most cases is
is due to over-flow-not boil away; therefore, antifreeze
recommended for year round service-especially since
and water are lost in the same proportions as originally
the widespread use of the pressurized cooling system as
installed.
well as air conditioning equipment.
In checking the protective strength of permanent
Ethylene glycol base antifreeze coolant is a product
antifreeze, the refractometer type tester is recommended
which contains a number of characteristics particularly
in preference over the hydrometer.
Refractometer
suited to protect against freezing, at the same time,
testers are usually accurate within about 1 F.
maintain compatibility with various kinds of metals as
Hydrometers are known to have a wide variation even
well as nonmetals such as gaskets, seals and other
when new and sometimes become inaccurate in the
nonmetallic materials. Other features include a high
course of time. In any event, use a tester known to be
boiling point, corrosion resistance, foam resistant, non-
reasonably accurate.
harmful to paint finishes and storage stability. These
Do not add rust inhibitors to permanent type
antifreezes are usually colored with a dye for
anitfreeze, since the antifreeze already contains specific
identification purposes, which in no way adversely affects
material for this purpose.
their use.
The addition of such additives may react undesirably with
Maintenance
additives already in the antifreeze. Never use additives
For best results, maintain at least a 33% (by volume)
containing soluble / oil with ethylene glycol antifreeze.
standard strength ethylene glycol antifreeze in the
Should conditions develop which would tend to cause
cooling system at all times.
foaming, the presence of soluble oil would aggravate the
The 33% mixture, with clean water, would be sufficient to
foaming.
protect the system down to 0* F.
The use of additives that are intended to improve
It is generally agreed that this is the minimum required to
heat transfer for the purpose of preventing engine
protect an engine (year around) against corrosion. The
overheating is not recommended. Tests have indicated
maintenance of a 33% solution also aids in the efficient
that there is as yet no additive that will increase heat
operation of the pressure type cooling system due to the
transfer. Furthermore, there is the possibility that the
higher boiling point of the antifreeze.
addition of such material might generate cooling system
Avoid an over-concentration of ethylene glycol
problems because of incompatibility with the carefully
permanent antifreeze mixture. A mixture of over 60%
formulated permanent antifreeze.
Regular periodic
(by volume) adversely affects freeze protection and heat
cooling system maintenance has proven to be the best
transfer rates. In general, a 60% mixture will protect to
way to insure efficient cooling.
temperatures as low as 60 F. Good practice would be to
To assure continued corrosion protection as well as
follow the instructions printed on containers, since the
efficient general cooling system efficiency, the
various products may vary somewhat in this respect.
permanent type antifreeze should be renewed (drain and
refill) once each year. This service should be performed
before cold weather. In any event, check the antifreeze
protection level before cold weather to safeguard against
freeze damage.
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